Aren't Yoda and Zuckuss considered in the "less common" group as well?
I think the old rarity scale might need to be revised abit as Vectis have had a lot of Yoda, Leia Bespin, IG88, TFP's etc. recently but very few of some others (don't remember seeing an ERG or Zuckuss @ Vectis and I also don't remember any first 12 on Tri cards).
It's a different discussion, but I wonder if they were batched up differently in some assortments. What I mean is perhaps the one's that we're seeing more of now (IG88, TFP, Leia Bespin, Yoda) are one distinct assortment, wheras first 12, ERG, Zuckuss etc. are in another distinct assortment. Remember the guy on FB with loads in his loft? He had a ton of Han original, Ben, C3PO(I think) so perhaps he had a different assortment to what Vectis recovered from Beeches.
It does seem notable that we're seeing large amounts of particular characters popping up in batches, rather than there being a more even distribution.